Digital projection technologies, such as Digital Light Processing (DLP) and Liquid Crystal Displays (LCD), are increasingly used in many non-traditional consumer, commercial and scientific applications. In computer graphics and vision, for instance, video projectors have recently been used as per-pixel controllable light sources for real-time shape acquisition and for complex appearance capture and control. Most of these applications require a projector to be focused for best performance. In practice, virtually all projectors are built with large apertures to maximize their brightness at the expense of narrower depths of field, and thus are designed to produce focused images on a single fronto-parallel screen, i.e., the traditional application for the projector.
In some applications, however, it is desirable to project an image onto non-planar structures, such as multiple planes or a dome, to create, for example, a virtual environment. In such cases, most parts of the projected image are blurred due to projection defocus, which results from narrow depth of field. One way to solve this problem is to design sophisticated optics for a particular projection structure onto which the image is projected. However, it is difficult to subsequently modify such optics to accommodate changes in the projection structure. Another approach is to use multiple projectors, where the number of depths for which the projected image can be in focus equals the number of projectors required. However, the number of projectors that must be used has to increase as the size and complexity of the projection structure increases.
In other applications, images projected by digital projectors often suffer from pixelation artifacts. Pixelation can be caused by two factors. The first is spatial digitization due to the finite resolution of the digital projectors. The second is the gap between adjacent pixels on the digital projector's physical image plane that arises because the pixel fill-factor is never complete. Pixelation tends to mark out pixel boundaries more distinctly when the resolution of images to be projected is much higher than the resolution of the digital projectors that are used to project the images.